Compression braking system for an internal combustion engine

ABSTRACT

A compression braking system for an internal combustion engine is provided which includes a compact housing disposed adjacent the fuel injecting actuating assembly and the exhaust valve actuating assembly for each cylinder of the engine. The housing is provided with a first cavity in which is reciprocally mounted a first piston having one end thereof protruding from one end of the first cavity and being engaged and moved by the fuel injecting actuating assembly. A second cavity is formed in the housing in a proximate angular relation with the first cavity. Reciprocally mounted within the second cavity is a second piston having one end thereof protruding from one end of the second cavity and engaging and moving the exhaust valve actuating assembly to releases compression pressure within the cylinder and provide retarding power when the engine is in the compression braking mode. A third cavity is provided within the housing which forms a linkage passage communicating with corresponding second ends of the first and second cavities. During normal operation of the engine, the linkage passage is substantially void of hydraulic fluid, thus motion of the first piston is not hydraulically transferred to the second piston. When the engine is in a compression braking mode, hydraulic fluid fills the linkage passage thereby causing the motion of the first piston to be hydraulically transferred through the linkage passage to the second piston and effect movement of the exhaust valve actuating assembly.

BACKGROUND OF THE INVENTION

Compression braking of an internal combustion engine is a well knownconcept for enhancing the braking effect of conventional braking systemsincorporated in heavy duty trucks, buses and the like. It has been foundthat the utilization of compression braking significantly reduces wearand stress on the conventional braking system and thus, reduces theincidents of failure of such braking systems. Various compressionbraking systems have heretofore been utilized; however, because ofcertain design characteristics, they have been beset with one or more ofthe following shortcomings: (a) an inordinate number of components arerequired thereby significantly increasing the complexity and initialcost of the system; (b) the system requires a large and sophisticatedhydraulic network; (c) certain of the system components are subjected tosevere moment and horizontal reaction forces thereby, resulting incomponents being bulky and thick in order to withstand such forces; (d)portions of the engine block and head must be redesigned orsignificantly modified to accommodate the compression braking system;(e) an inordinate amount of space is required to house an engine with aprior compression braking system mounted thereon; (f) the compressionbraking system is unreliable and requires frequent servicing andadjusting; (g) various components of the system require precise fittingand thus close manufacturing tolerances in order for the system to be inproper working order; and (h) installation of the compression brakingsystem on the engine block or cylinder head is a time-consuming, awkwardand difficult operation.

SUMMARY OF THE INVENTION

Thus, it is an object of the invention to provide a compression brakingsystem which overcomes the aforementioned shortcomings of the priorsystems.

It is a further object to provide a compression braking system having asimple, compact housing wherein no excessive or abnormal moment orhorizontal reaction forces are created therein when the engine is in thecompression braking mode.

It is a further object to provide a compression braking system which maybe utilized in either in-line or V-type engines or in single or multiplecylinder head engines.

Further and additional objects will appear from the description,accompanying drawing and appended claims.

In accordance with one embodiment of the invention, a compressionbraking system for an internal combustion engine is provided having acompact housing which is adapted to be disposed proximate the fuelinjecting actuating assembly and the exhaust valve actuating assemblyprovided for each cylinder of the engine. The housing includes a firstcavity in which is reciprocally mounted a first piston. One end of thefirst piston protrudes from one end of the cavity and is engaged andmoved inwardly by the fuel injecting actuating assembly. A second cavityis formed in the housing and is in angular proximate relation with thefirst cavity. Reciprocally mounted within the second cavity is a secondpiston having one end protruding from one end of the second cavity andbeing adapted to engage and move the exhaust valve actuating assemblywhen the engine is in the compression braking mode. The housing isprovided with a third cavity having a section thereof forming a linkagepassage interconnecting corresponding second ends of the first andsecond cavities. Disposed within the third cavity is a connector piecehaving a portion thereof communicating with an engine circuit throughwhich hydraulic fluid flows. Also mounted within the housing thirdcavity and disposed between the connector piece and the linkage passageis a check valve. The check valve allows hydraulic fluid to only flowfrom the circuit into the linkage passage and fill the same with saidhydraulic fluid. When the linkage passage is filled with the hydraulicfluid, motion of the first piston is hydraulically transferred to thesecond piston. Filling of the linkage passage occurs when the engine isin the compression braking mode. During normal operation of the engine,the hydraulic fluid is drained from the linkage passage.

DESCRIPTION

For a more complete understanding of the invention, reference is made tothe drawings wherein:

FIG. 1 is a fragmentary top plan view of an internal combustion engineshowing one embodiment of the improved compression braking systemmounted thereon.

FIG. 2 is an enlarged fragmentary side elevational view of a segment ofthe compression braking system shown in FIG. 1 with a portion of thefuel injecting actuating assembly removed.

FIG. 3 is a fragmentary sectional view taken along line 3--3 of FIG. 1.

FIG. 4 is a diagrammatic view of the hydraulic fluid network for thecompression braking system.

FIG. 5 is an enlarged fragmentary view of a dump valve which is anoptional component of the network of FIG. 4.

Referring now to the drawings and more particularly to FIG. 1, apreferred embodiment of the improved compression braking system 10 isshown mounted on the cylinder head H of a conventional in-line engine E.While FIG. 1 and FIG. 2, as well, appear to show an overhead camshaftengine it is to be understood that the invention hereinafter describedis not intended to be limited thereto but may be incorporated in anengine having a lower mounted camshaft DHR and associated push rods.

The engine as illustrated in FIG. 1 includes an exhaust valve rocker armassembly 11, a fuel injector rocker arm assembly 12 and an air intakevalve rocker arm assembly 13. The three assemblies 11-13 are normallyprovided for each cylinder, not shown, of the engine. Each assemblyincludes a rocker arm R which is mounted on the exterior of the cylinderhead for pivoting about a fixed axis X which may be locatedapproximately midlength of the arm see FIG. 2. One end R₂ of each arm isadapted to be engaged by a camshaft, not shown. The opposite end R₁ ofeach rocker arm is adapted to perform a particular function. In the caseof assembly 11, the arm end R₁ is adapted to engage the exhaust valves,not shown, mounted adjacent the upper end of the cylinder. The exhaustvalves are biased to normally assume a closed position and thus,assembly 11 actuates the exhaust valves to an open position inaccordance with a predetermined time sequence. Arm end R₁ of assembly 12is adapted to actuate the fuel injector, not shown, provided for thecylinder. Rocker arm R of assembly 12 would normally be aligned with thecenterline of the cylinder. Arm end R₁ of assembly 13 is adapted toengage and actuate the air intake valves, not shown, of the cylinder.Normally a pair of exhaust valves and a pair of air intake valves areprovided for each cylinder; thus, the arm ends R₁ of assemblies 11 and13 are provided with a suitable bridge which will effect simultaneousoperation of the valves comprising each pair.

As seen in FIG. 2 and 3, the compression braking system 10 includes acompact housing 14 which is mounted on a rocker shaft support B formedon head H. The housing is sized so that it may be readily locatedbetween the arms R of assemblies 11,12 without obstructing movementthereof. Housing 14 is provided with a first cavity 15 in which isreciprocally mounted a first piston 16 sometimes referred to as themaster piston. One end 16a of the piston protrudes from one end 15a ofcavity 15 and is adapted to be engaged by a lateral projection 12Aformed on the side of the rocker arm of assembly 12. Housing 14 is alsoprovided with a second cavity 17 which is disposed at an angular,proximate position with respect to cavity 5. Reciprocally mounted withincavity 17 is a second piston 18, sometimes referred to as the slavepiston. Piston 18 has a portion 18a thereof which protrudes outwardlyfrom one end 17a of cavity 17 and is adapted to engage and push againsta lateral projection llA formed on the side of the rocker arm ofassembly 11, when the engine is in a compression braking mode, as willbe described more fully hereinafter.

As seen in FIG. 3, the protruding piston portion 18a is provided with alaterally extending annular collar C which limits the extent to whichthe piston 18 can be retracted into cavity 17. The portion 18b of thepiston which projects into cavity 17 is provided with an annularexternal groove G in which will flow hydraulic fluid when the pistonportion is disposed within cavity 17 and the fluid is urging the piston18 to move outwardly, as will be described more fully hereinafter.

Corresponding inner, or second, ends 15b, 17b of cavities 15 and 17,respectively, are interconnected by a linkage passage 20a which forms asection of a third cavity 20 provided in housing 14. It should be notedthat cavity 20 is located between cavities 15 and 17 has mounted at oneend 20b, a connector piece 21. Piece 21 has an elongated first section21a which is threaded into the cavity end 20b. Section 21a is providedwith a longitudinally extending internal passage or bore 21b having anouter end thereof terminating in an exposed second section 21c. Section21c is provided with an internal cross passage 21d which communicateswith the outer end of passage 21b. An annular internal passage 21e,formed in piece section 21c, encompasses cross passage 21d and the upperend of passage 21b and communicates with opposite ends thereof. Suitableports 21f are provided in the exposed piece section 21c for connectingthe passage 21e to a circuit or network N of the engine through whichhydraulic fluid subjected to a predetermined pressure range flows whenthe engine is operating under normal conditions. The network to behereinafter described, is diagrammatically shown in FIG. 4.

Positioned within housing cavity 20 and located between linkage passage20a and the concealed end of piece section 21a is a ball-type checkvalve 22. The ball 22a of the valve is urged by a spring 22b intoengagement with a seat which is provided at the end of piece section 21aand thus, closes off passage 21b except when the hydraulic fluidpressure within network N overcomes for a predetermined time interval,the bias of spring 22b. When the ball 22a is unseated, hydraulic fluidwill completely fill linkage passage 20a and the portions of cavities 15and 17 connected thereto. The unseating hydraulic fluid pressure occursfor the short period of time within the network N when braking of engineis initiated. As the braking action continues, the master piston 16 willbe moved by the rocker arm R of assembly 12, which is actuated by thepush rod engaging the engine cam shaft. Once the linkage passage isfilled with hydraulic fluid and the master piston 16 is beginning to bepushed into the cavity, the pressure within passage 20a, coupled withthe spring pressure on the ball, will cause the latter to quicklyreseat. When this latter condition occurs, the movement of the masterpiston towards the cavity end 15b will be hydraulically transferred tothe concealed end of slave piston 18 causing the latter to be pushedoutwardly a predetermined amount whereupon the actuating assembly 11will cause the exhaust valves to open and remain open thereby releasingcompression pressure within the engine cylinder and provide retardingpower for the engine while the engine remains in the compression brakingmode. The slave piston will continue its outward movement in response tothe movement of the master piston until the external groove G of piston18 moves beyond the end 17a of cavity 17. Once groove G is exposed, thehydraulic fluid within passage 20a will flow out through groove G. Thereis sufficient clearance between the wall of cavity 17 and the exteriorsurface of the portion 18b of piston 18 disposed between the groove andthe end of the piston adjacent the cavity end 17b, to allow the fluid toflow to groove G. Thus, the groove placement on the piston exteriordetermines the limit to which the slave piston 18 can be moved outwardlyby the master piston 16.

Once braking of the engine has been discontinued, the fluid withinpassage 20a and the portions of the cavities communicating therewithwill drain a sufficient amount of fluid so that there is no longerresponsive movement of the slave piston because there is insufficientfluid within the passage to provide a consistent, uniform hydraulicfluid linkage between the two pistons. As the master piston 16 isactuated by the rocker arm of assembly 12, the piston 16 will causewhatever hydraulic fluid remaining in passage 20a to substantially draintherefrom in a short period of time.

If a more rapid drainage from the linkage passage is desired, anoptional spool-type dump valve 23, see FIGS. 4 and 5 may be utilized.Valve 23, as seen in FIG. 5, is of conventional design and includes aspool or shuttle 24 which is reciprocally mounted within a bore 25formed in a casing 26. The lower end 25a of the bore is closed and isengaged by one end of a coil spring 27. The opposite end of the springengages the lower end 24a of spool 24. Spring 27 biases the spool toassume its normal rest position, as seen in FIG. 5. When in the restposition, an annular groove 24b formed on the exterior of the spool issubstantially centered with respect to a pair of opposed ports 28,30formed in casing 26. Port 28 communicates via conduit 31 with theportion of the third cavity 20 located between the check valve ball 22aand the linkage passage 20a. Port 30 communicates with a sump 32, seeFIG. 4. The upper end 25b of the bore is connected via conduit 33 to aportion of the network N which is upstream of check valve 22. Thus, whenthe pressure of the hydraulic fluid in the network N exceeds the bias ofspring 27, the spool 24 will be forced towards the bore closed end 25acompressing spring 27 and causing the groove 24b of the spool to be outof alignment with ports 28,30 and interrupting communication between thethird cavity 20 of housing 14 and the sump 32.

The network N, as shown diagrammatically in FIG. 4, includes a solenoidvalve control 34 which is located in a segment of the hydraulic fluidcircuit between a source 35 of pressurized hydraulic fluid and thecompression braking system 10 located in proximate relation to eachcylinder of the engine. The control 34 is connected in such a way thatwhen the brake pedal or lever, not shown, is actuated to effect braking,the control 34 will complete the flow circuit between the source 35 andthe respective compression braking systems 10. When this occurs,hydraulic fluid pressure will cause the check valve ball 22a in eachinstance to unseat allowing the linkage passage 20a to be filled withthe required amount of fluid. As forenoted, once the linkage passage isproperly filled with hydraulic fluid, motion of the master piston 16retracting into cavity 15 will be hydraulically transferred to the slavepiston 18.

The compactness of housing 14 is accomplished by reason of the relativelocations of the cavities 15, 17 and 20. The angled disposition of themaster and slave pistons results in the horizontal or transversecomponents of the forces generated within the housing by the pistonscancelling one another leaving only a vertical or aligned componentwhich is effectively resisted by anchor bolts 36. Furthermore, the linesof motion of the pistons 16,18 are spaced sufficiently from points ofattachment of the housing 14 to the support B that the moments producedby such piston movement are cancelled. In FIG. 2, only one anchor bolt36 is shown which extends through a laterally extending lug 37 formed onthe exterior of housing 14, and is threaded into the portion of supportB subtending the lug. The housing 14 is normally provided with a pair ofdiametrically opposed lugs.

While the improved compression braking system has been described inrelation to an in-line engine, it is not intended to be limited thereto.Such a system can be readily installed in a V-type engine or in engineshaving single or multiple heads. The number of cylinders and thehorsepower rating of the engine may also vary over a wide range.

I claim:
 1. In a multi-cylinder internal combustion engine having fuelinjecting means for each cylinder, first actuating means for operatingthe fuel injecting means, exhaust valve means for each cylinder biasedto assume a closed position, and second actuating means for opening theexhaust valve means; a compression braking system comprising a housingfor disposition proximate the first and second actuating means of eachcylinder, said housing including a first cavity in which a first pistonis reciprocally mounted, a portion of said first piston protruding fromone end of the first cavity and being engaged and moved by said firstactuating means, a second cavity angularly disposed relative to saidfirst cavity and proximate a second end of said first cavity, a secondpiston reciprocally mounted within said second cavity and having aportion thereof protruding from one end of the second cavity forengaging and moving the second actuating means when the engine is in acompression braking mode, and a third cavity proximate said first andsecond cavities and having a portion thereof forming a linkage passageinterconnecting a second end of the second cavity to the second end ofthe first cavity; normally closed check valve means disposed within saidthird cavity; a connector piece having a first section provided with anelongated first passage and disposed within said third cavity and on theopposite side of said check valve means from the linkage passage, and aprotruding second section having a second passage communicating with thefirst passage formed in said first section, said second passage forminga segment of a flow circuit through which hydraulic fluid circulates;during a predetermined engine operating mode, said linkage passage beingfilled with hydraulic fluid from the flow circuit whereby inwardmovement of said first piston into the said first cavity is transmittedvia the linkage passage hydraulic fluid to said second piston affectingoutward movement thereof whereby said second actuating means opens thecylinder exhaust valve means.
 2. The compression braking system of claim1 wherein upon the second piston having moved outwardly relative to thesecond cavity a predetermined amount further outward movement of saidsecond piston is automatically discontinued.
 3. The compression brakingsystem of claim 1 wherein the first piston functions as a master pistonand the second piston functions as a slave piston when the engine is inthe braking mode and until the second piston has moved a predetermineddistance outwardly relative to the second cavity.
 4. The compressionbraking system of claim 2 wherein the second piston has a second portiondisposed within said second cavity, said second portion being providedwith an external groove in continuous communication with the linkagepassageway, when said groove is disposed within said second cavity; saidgroove being disposed substantially outwardly of said second cavity whensaid second piston has moved outwardly said predetermined amount wherebyfurther outward movement of said second piston in response to movementof said first piston is discontinued.
 5. The compression braking systemof claim 4 wherein the protruding portion of the second piston isprovided with an exposed external collar impassable relative to the oneend of the second cavity.
 6. The compression braking system of claim 1wherein the relative angular proximate locations of the first, secondand third cavities within the housing and the directions of movement ofthe pistons within said first and second cavities effect substantialcancellation of transverse forces generated by said pistons when theengine is operating in the compression braking mode.